This invention relates to a hydraulic impact hammer, particularly to the frame structure of an impact hammer, where the housing guiding the piston of the impact hammer is separated from the housing surrounding the impact member, so that the tension wave reflected from the impact member is prevented from proceeding to other parts of the hammer.
Impact hammers are divided, on the basis of their operating power for instance, into two main groups, i.e. pneumatic impact hammers and hydraulic impact hammers. The power of a pneumatic impact hammer is substantially lower than that of a hydraulic impact hammer. Likewise, pneumatic impact hammers are normally hand held, whereas hydraulic impact hammers are generally used in connection with various machines. For example, a hydraulic impact hammer may be used in drilling tunnels through rock, in which case the hammer is mounted on a carriage for advancing the hammer as the rock is broken and removed. In both hydraulic impact hammers and pneumatic impact hammers, a tension wave is reflected to other parts of the device. The DE patent 805,268 suggests an arrangement for reducing the effect of this tension wave. In DE 805,268, the guide ring of the impact member is made of elastic material. Moreover, the collar supporting the impact member is made of attenuating material. A similar structure is described in DE 805,748.
In a known hydraulic impact hammer, the housing or frame elements of the impact hammer, including a control valve system and valve housings of hydraulic fluid, a piston and a member guiding the piston, various sealing rings and a member guiding the impact member, are permanently interconnected either with long binding screws or with several shorter bolts. This structure is mounted inside a casing by means of attenuating elements provided around the impact hammer. The joining of the housing elements to each other causes various heavy strains on the whole impact hammer. Thus, the masses to be attenuated are large, which applies heavy loads to the various housing elements, and particularly to the members that interconnect the housing elements, i.e. the above mentioned screws or bolts. In similar fashion, in operation the junction surfaces of the impact hammer are in sliding contact with each other and are subjected to wear. Moreover, the tension wave reflected from the impact member is transmitted to the housing structure, which causes extra strains to other housing elements, as well as vibration and noise. The use of binding screws as the members that interconnect the housing elements also causes distortion in the housing elements and the binding screws themselves may be distorted, e.g. bent. Such distortions make the maintenance of the impact hammer difficult, in particular because it leads to difficulty in dismantling and re-assembling the interconnected elements.